Multi-radio coexistence

ABSTRACT

In a mobile device capable of wireless communications using multiple radio access technologies (RATs), transmit communications of one RAT may cause interference with receive communications of another RAT. In the case of wireless local area network (WLAN) communications, a CTS-to-Self message may control the timing of WLAN communications such that WLAN receptions do not overlap with transmissions of another RAT, such as a Long Term Evolution (LTE) radio. The CTS-to-Self message timing control may be executed by a mobile device operating as a WLAN access point.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 61/495,696 entitled “MULTI-RADIO COEXISTENCE,” filedJun. 10, 2011, and U.S. Provisional Patent Application No. 61/469,784entitled “ADVANCED COEXISTENCE DESIGN,” filed Mar. 30, 2011, thedisclosures of which are expressly incorporated by reference herein intheir entireties.

TECHNICAL FIELD

The present description is related, generally, to multi-radio techniquesand, more specifically, to coexistence techniques for multi-radiodevices.

BACKGROUND

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, data, and so on. Thesesystems may be multiple-access systems capable of supportingcommunication with multiple users by sharing the available systemresources (e.g., bandwidth and transmit power). Examples of suchmultiple access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE)systems, and orthogonal frequency division multiple access (OFDMA)systems.

Generally, a wireless multiple-access communication system cansimultaneously support communication for multiple wireless terminals.Each terminal communicates with one or more base stations viatransmissions on the forward and reverse links. The forward link (ordownlink) refers to the communication link from the base stations to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the base stations. This communication linkmay be established via a single-in-single-out, multiple-in-single-out ora multiple-in-multiple out (MIMO) system.

Some conventional advanced devices include multiple radios fortransmitting/receiving using different Radio Access Technologies (RATs).Examples of RATs include, e.g., Universal Mobile TelecommunicationsSystem (UMTS), Global System for Mobile Communications (GSM), cdma2000,WiMAX, WLAN (e.g., WiFi), Bluetooth, LTE, and the like.

An example mobile device includes an LTE User Equipment (UE), such as afourth generation (4G) mobile phone. Such 4G phone may include variousradios to provide a variety of functions for the user. For purposes ofthis example, the 4G phone includes an LTE radio for voice and data, anIEEE 802.11 (WiFi) radio, a Global Positioning System (GPS) radio, and aBluetooth radio, where two of the above or all four may operatesimultaneously. While the different radios provide usefulfunctionalities for the phone, their inclusion in a single device givesrise to coexistence issues. Specifically, operation of one radio may insome cases interfere with operation of another radio through radiative,conductive, resource collision, and/or other interference mechanisms.Coexistence issues include such interference.

This is especially true for the LTE uplink channel, which is adjacent tothe Industrial Scientific and Medical (ISM) band and may causeinterference therewith. It is noted that Bluetooth and some Wireless LAN(WLAN) channels fall within the ISM band. In some instances, a Bluetootherror rate can become unacceptable when LTE is active in some channelsof Band 7 or even Band 40 for some Bluetooth channel conditions. Eventhough there is no significant degradation to LTE, simultaneousoperation with Bluetooth can result in disruption in voice servicesterminating in a Bluetooth headset. Such disruption may be unacceptableto the consumer. A similar issue exists when LTE transmissions interferewith GPS. Currently, there is no mechanism that can solve this issuesince LTE by itself does not experience any degradation

With reference specifically to LTE, it is noted that a UE communicateswith an evolved NodeB (eNB; e.g., a base station for a wirelesscommunications network) to inform the eNB of interference seen by the UEon the downlink. Furthermore, the eNB may be able to estimateinterference at the UE using a downlink error rate. In some instances,the eNB and the UE can cooperate to find a solution that reducesinterference at the UE, even interference due to radios within the UEitself. However, in conventional LTE, the interference estimatesregarding the downlink may not be adequate to comprehensively addressinterference.

In one instance, an LTE uplink signal interferes with a Bluetooth signalor WLAN signal. However, such interference is not reflected in thedownlink measurement reports at the eNB. As a result, unilateral actionon the part of the UE (e.g., moving the uplink signal to a differentchannel) may be thwarted by the eNB, which is not aware of the uplinkcoexistence issue and seeks to undo the unilateral action. For instance,even if the UE re-establishes the connection on a different frequencychannel, the network can still handover the UE back to the originalfrequency channel that was corrupted by the in-device interference. Thisis a likely scenario because the desired signal strength on thecorrupted channel may sometimes be higher than reflected in themeasurement reports of the new channel based on Reference SignalReceived Power (RSRP) to the eNB. Hence, a ping-pong effect of beingtransferred back and forth between the corrupted channel and the desiredchannel can happen if the eNB uses RSRP reports to make handoverdecisions.

Other unilateral action on the part of the UE, such as simply stoppinguplink communications without coordination of the eNB may cause powerloop malfunctions at the eNB. Additional issues that exist inconventional LTE include a general lack of ability on the part of the UEto suggest desired configurations as an alternative to configurationsthat have coexistence issues. For at least these reasons, uplinkcoexistence issues at the UE may remain unresolved for a long timeperiod, degrading performance and efficiency for other radios of the UE.

SUMMARY

Offered is a method for wireless communications. The method includesactively communicating on a first radio access technology (RAT) as partof an end-to-end communication link. The method also includes activelycommunicating on a second RAT as part of the end-to-end communicationlink. The method further includes sending a message instructing a remotedevice on the second RAT to temporarily stop transmission. The messageis sent at a time calculated to prevent transmission from the remotedevice from being received during an uplink transmission of the firstRAT in the end-to-end communication link.

Offered is an apparatus for wireless communications. The apparatusincludes means for actively communicating on a first radio accesstechnology (RAT) as part of an end-to-end communication link. Theapparatus also includes means for actively communicating on a second RATas part of the end-to-end communication link. The apparatus furtherincludes means for sending a message instructing a remote device on thesecond RAT to temporarily stop transmission. The message is sent at atime calculated to prevent transmission from the remote device frombeing received during an uplink transmission of the first RAT in theend-to-end communication link.

Offered is a computer program product configured for wirelesscommunications. The computer program product includes a non-transitorycomputer-readable medium having non-transitory program code recordedthereon. The program code includes program code to actively communicateon a first radio access technology (RAT) as part of an end-to-endcommunication link. The program code also includes program code toactively communicate on a second RAT as part of the end-to-endcommunication link. The program code further includes program code tosend a message instructing a remote device on the second RAT totemporarily stop transmission. The message is sent at a time calculatedto prevent transmission from the remote device from being receivedduring an uplink transmission of the first RAT in the end-to-endcommunication link.

Offered is an apparatus for wireless communications. The apparatusincludes a memory and a processor(s) coupled to the memory. Theprocessor(s) is configured to actively communicate on a first radioaccess technology (RAT) as part of an end-to-end communication link. Theprocessor(s) is also configured to actively communicate on a second RATas part of the end-to-end communication link. The processor(s) isfurther configured to send a message instructing a remote device on thesecond RAT to temporarily stop transmission. The message is sent at atime calculated to prevent transmission from the remote device frombeing received during an uplink transmission of the first RAT in theend-to-end communication link.

Additional features and advantages of the disclosure will be describedbelow. It should be appreciated by those skilled in the art that thisdisclosure may be readily utilized as a basis for modifying or designingother structures for carrying out the same purposes of the presentdisclosure. It should also be realized by those skilled in the art thatsuch equivalent constructions do not depart from the teachings of thedisclosure as set forth in the appended claims. The novel features,which are believed to be characteristic of the disclosure, both as toits organization and method of operation, together with further objectsand advantages, will be better understood from the following descriptionwhen considered in connection with the accompanying figures. It is to beexpressly understood, however, that each of the figures is provided forthe purpose of illustration and description only and is not intended asa definition of the limits of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, nature, and advantages of the present disclosure willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout.

FIG. 1 illustrates a multiple access wireless communication systemaccording to one aspect.

FIG. 2 is a block diagram of a communication system according to oneaspect.

FIG. 3 illustrates an exemplary frame structure in downlink Long TermEvolution (LTE) communications.

FIG. 4 is a block diagram conceptually illustrating an exemplary framestructure in uplink Long Term Evolution (LTE) communications.

FIG. 5 illustrates an example wireless communication environment.

FIG. 6 is a block diagram of an example design for a multi-radiowireless device.

FIG. 7 is graph showing respective potential collisions between sevenexample radios in a given decision period.

FIG. 8 is a diagram showing operation of an example Coexistence Manager(C×M) over time.

FIG. 9 is a block diagram illustrating adjacent frequency bands.

FIG. 10 is a block diagram of a system for providing support within awireless communication environment for multi-radio coexistencemanagement according to one aspect of the present disclosure.

FIG. 11 is a diagram of an exemplary mobile device configuration.

FIG. 12 is a diagram illustrating wireless communication according toone aspect of the present disclosure.

FIG. 13 is a block diagram illustrating coexistence management accordingto one aspect of the present disclosure.

FIG. 14 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing coexistence managementaccording to one aspect of the present disclosure.

DETAILED DESCRIPTION

Various aspects of the disclosure provide techniques to mitigatecoexistence issues in multi-radio devices, where significant in-devicecoexistence problems can exist between multiple radio accesstechnologies (RATs), e.g., the LTE and Industrial Scientific and Medical(ISM) bands (e.g., for BT/WLAN). In such mobile devices, transmitcommunications of one RAT may cause interference with receivecommunications of another RAT. In the case of wireless local areanetwork (WLAN) communications, a CTS-to-Self message may control thetiming of WLAN communications such that WLAN receptions do not overlapwith transmissions of another RAT, such as a Long Term Evolution (LTE)radio. The CTS-to-Self message timing control may be executed by amobile device operating as a WLAN access point as described below.

The techniques described herein can be used for various wirelesscommunication networks such as Code Division Multiple Access (CDMA)networks, Time Division Multiple Access (TDMA) networks, FrequencyDivision Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA)networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms“networks” and “systems” are often used interchangeably. A CDMA networkcan implement a radio technology such as Universal Terrestrial RadioAccess (UTRA), cdma2000, etc. UTRA includes Wideband-CDMA (W-CDMA) andLow Chip Rate (LCR). cdma2000 covers IS-2000, IS-95 and IS-856standards. A TDMA network can implement a radio technology such asGlobal System for Mobile Communications (GSM). An OFDMA network canimplement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11,IEEE 802.16, IEEE 802.20, Flash-OFDM®, etc. UTRA, E-UTRA, and GSM arepart of Universal Mobile Telecommunication System (UMTS). Long TermEvolution (LTE) is an upcoming release of UMTS that uses E-UTRA. UTRA,E-UTRA, GSM, UMTS and LTE are described in documents from anorganization named “3rd Generation Partnership Project” (3GPP). CDMA2000is described in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). These various radio technologies andstandards are known in the art. For clarity, certain aspects of thetechniques are described below for LTE, and LTE terminology is used inportions of the description below.

Single carrier frequency division multiple access (SC-FDMA), whichutilizes single carrier modulation and frequency domain equalization isa technique that can be utilized with various aspects described herein.SC-FDMA has similar performance and essentially the same overallcomplexity as those of an OFDMA system. SC-FDMA signal has lowerpeak-to-average power ratio (PAPR) because of its inherent singlecarrier structure. SC-FDMA has drawn great attention, especially in theuplink communications where lower PAPR greatly benefits the mobileterminal in terms of transmit power efficiency. It is currently aworking assumption for an uplink multiple access scheme in 3GPP LongTerm Evolution (LTE), or Evolved UTRA.

Referring to FIG. 1, a multiple access wireless communication systemaccording to one aspect is illustrated. An evolved Node B 100 (eNB)includes a computer 115 that has processing resources and memoryresources to manage the LTE communications by allocating resources andparameters, granting/denying requests from user equipment, and/or thelike. The eNB 100 also has multiple antenna groups, one group includingantenna 104 and antenna 106, another group including antenna 108 andantenna 110, and an additional group including antenna 112 and antenna114. In FIG. 1, only two antennas are shown for each antenna group,however, more or fewer antennas can be utilized for each antenna group.A User Equipment (UE) 116 (also referred to as an Access Terminal (AT))is in communication with antennas 112 and 114, while antennas 112 and114 transmit information to the UE 116 over a downlink (DL) 120 andreceive information from the UE 116 over an uplink (UL) 118. The UE 122is in communication with antennas 106 and 108, while antennas 106 and108 transmit information to the UE 122 over a downlink (DL) 126 andreceive information from the UE 122 over an uplink 124. In a frequencydivision duplex (FDD) system, communication links 118, 120, 124 and 126can use different frequencies for communication. For example, thedownlink 120 can use a different frequency than used by the uplink 118.

Each group of antennas and/or the area in which they are designed tocommunicate is often referred to as a sector of the eNB. In this aspect,respective antenna groups are designed to communicate to UEs in a sectorof the areas covered by the eNB 100.

In communication over the downlinks 120 and 126, the transmittingantennas of the eNB 100 utilize beamforming to improve thesignal-to-noise ratio of the uplinks for the different UEs 116 and 122.Also, an eNB using beamforming to transmit to UEs scattered randomlythrough its coverage causes less interference to UEs in neighboringcells than a UE transmitting through a single antenna to all its UEs.

An eNB can be a fixed station used for communicating with the terminalsand can also be referred to as an access point, base station, or someother terminology. A UE can also be called an access terminal, awireless communication device, terminal, or some other terminology.

FIG. 2 is a block diagram of an aspect of a transmitter system 210 (alsoknown as an eNB) and a receiver system 250 (also known as a UE) in aMIMO system 200. In some instances, both a UE and an eNB each have atransceiver that includes a transmitter system and a receiver system. Atthe transmitter system 210, traffic data for a number of data streams isprovided from a data source 212 to a transmit (TX) data processor 214.

A MIMO system employs multiple (NT) transmit antennas and multiple (NR)receive antennas for data transmission. A MIMO channel formed by the NTtransmit and NR receive antennas may be decomposed into NS independentchannels, which are also referred to as spatial channels, whereinNS≦min{NT, NR}. Each of the NS independent channels corresponds to adimension. The MIMO system can provide improved performance (e.g.,higher throughput and/or greater reliability) if the additionaldimensionalities created by the multiple transmit and receive antennasare utilized.

A MIMO system supports time division duplex (TDD) and frequency divisionduplex (FDD) systems. In a TDD system, the uplink and downlinktransmissions are on the same frequency region so that the reciprocityprinciple allows the estimation of the downlink channel from the uplinkchannel. This enables the eNB to extract transmit beamforming gain onthe downlink when multiple antennas are available at the eNB.

In an aspect, each data stream is transmitted over a respective transmitantenna. The TX data processor 214 formats, codes, and interleaves thetraffic data for each data stream based on a particular coding schemeselected for that data stream to provide coded data.

The coded data for each data stream can be multiplexed with pilot datausing OFDM techniques. The pilot data is a known data pattern processedin a known manner and can be used at the receiver system to estimate thechannel response. The multiplexed pilot and coded data for each datastream is then modulated (e.g., symbol mapped) based on a particularmodulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM) selected for thatdata stream to provide modulation symbols. The data rate, coding, andmodulation for each data stream can be determined by instructionsperformed by a processor 230 operating with a memory 232.

The modulation symbols for respective data streams are then provided toa TX MIMO processor 220, which can further process the modulationsymbols (e.g., for OFDM). The TX MIMO processor 220 then provides NTmodulation symbol streams to NT transmitters (TMTR) 222 a through 222 t.In certain aspects, the TX MIMO processor 220 applies beamformingweights to the symbols of the data streams and to the antenna from whichthe symbol is being transmitted.

Each transmitter 222 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. NTmodulated signals from the transmitters 222 a through 222 t are thentransmitted from NT antennas 224 a through 224 t, respectively.

At a receiver system 250, the transmitted modulated signals are receivedby NR antennas 252 a through 252 r and the received signal from eachantenna 252 is provided to a respective receiver (RCVR) 254 a through254 r. Each receiver 254 conditions (e.g., filters, amplifies, anddownconverts) a respective received signal, digitizes the conditionedsignal to provide samples, and further processes the samples to providea corresponding “received” symbol stream.

An RX data processor 260 then receives and processes the NR receivedsymbol streams from NR receivers 254 based on a particular receiverprocessing technique to provide NR “detected” symbol streams. The RXdata processor 260 then demodulates, deinterleaves, and decodes eachdetected symbol stream to recover the traffic data for the data stream.The processing by the RX data processor 260 is complementary to theprocessing performed by the TX MIMO processor 220 and the TX dataprocessor 214 at the transmitter system 210.

A processor 270 (operating with a memory 272) periodically determineswhich pre-coding matrix to use (discussed below). The processor 270formulates an uplink message having a matrix index portion and a rankvalue portion.

The uplink message can include various types of information regardingthe communication link and/or the received data stream. The uplinkmessage is then processed by a TX data processor 238, which alsoreceives traffic data for a number of data streams from a data source236, modulated by a modulator 280, conditioned by transmitters 254 athrough 254 r, and transmitted back to the transmitter system 210.

At the transmitter system 210, the modulated signals from the receiversystem 250 are received by antennas 224, conditioned by receivers 222,demodulated by a demodulator 240, and processed by an RX data processor242 to extract the uplink message transmitted by the receiver system250. The processor 230 then determines which pre-coding matrix to usefor determining the beamforming weights, then processes the extractedmessage.

FIG. 3 is a block diagram conceptually illustrating an exemplary framestructure in downlink Long Term Evolution (LTE) communications. Thetransmission timeline for the downlink may be partitioned into units ofradio frames. Each radio frame may have a predetermined duration (e.g.,10 milliseconds (ms)) and may be partitioned into 10 subframes withindices of 0 through 9. Each subframe may include two slots. Each radioframe may thus include 20 slots with indices of 0 through 19. Each slotmay include L symbol periods, e.g., 7 symbol periods for a normal cyclicprefix (as shown in FIG. 3) or 6 symbol periods for an extended cyclicprefix. The 2L symbol periods in each subframe may be assigned indicesof 0 through 2L−1. The available time frequency resources may bepartitioned into resource blocks. Each resource block may cover Nsubcarriers (e.g., 12 subcarriers) in one slot.

In LTE, an eNB may send a Primary Synchronization Signal (PSS) and aSecondary Synchronization Signal (SSS) for each cell in the eNB. The PSSand SSS may be sent in symbol periods 6 and 5, respectively, in each ofsubframes 0 and 5 of each radio frame with the normal cyclic prefix, asshown in FIG. 3. The synchronization signals may be used by UEs for celldetection and acquisition. The eNB may send a Physical Broadcast Channel(PBCH) in symbol periods 0 to 3 in slot 1 of subframe 0. The PBCH maycarry certain system information.

The eNB may send a Cell-specific Reference Signal (CRS) for each cell inthe eNB. The CRS may be sent in symbols 0, 1, and 4 of each slot in caseof the normal cyclic prefix, and in symbols 0, 1, and 3 of each slot incase of the extended cyclic prefix. The CRS may be used by UEs forcoherent demodulation of physical channels, timing and frequencytracking, Radio Link Monitoring (RLM), Reference Signal Received Power(RSRP), and Reference Signal Received Quality (RSRQ) measurements, etc.

The eNB may send a Physical Control Format Indicator Channel (PCFICH) inthe first symbol period of each subframe, as seen in FIG. 3. The PCFICHmay convey the number of symbol periods (M) used for control channels,where M may be equal to 1, 2 or 3 and may change from subframe tosubframe. M may also be equal to 4 for a small system bandwidth, e.g.,with less than 10 resource blocks. In the example shown in FIG. 3, M=3.The eNB may send a Physical HARQ Indicator Channel (PHICH) and aPhysical Downlink Control Channel (PDCCH) in the first M symbol periodsof each subframe. The PDCCH and PHICH are also included in the firstthree symbol periods in the example shown in FIG. 3. The PHICH may carryinformation to support Hybrid Automatic Repeat Request (HARQ). The PDCCHmay carry information on resource allocation for UEs and controlinformation for downlink channels. The eNB may send a Physical DownlinkShared Channel (PDSCH) in the remaining symbol periods of each subframe.The PDSCH may carry data for UEs scheduled for data transmission on thedownlink. The various signals and channels in LTE are described in 3GPPTS 36.211, entitled “Evolved Universal Terrestrial Radio Access(E-UTRA); Physical Channels and Modulation,” which is publiclyavailable.

The eNB may send the PSS, SSS and PBCH in the center 1.08 MHz of thesystem bandwidth used by the eNB. The eNB may send the PCFICH and PHICHacross the entire system bandwidth in each symbol period in which thesechannels are sent. The eNB may send the PDCCH to groups of UEs incertain portions of the system bandwidth. The eNB may send the PDSCH tospecific UEs in specific portions of the system bandwidth. The eNB maysend the PSS, SSS, PBCH, PCFICH and PHICH in a broadcast manner to allUEs, may send the PDCCH in a unicast manner to specific UEs, and mayalso send the PDSCH in a unicast manner to specific UEs.

A number of resource elements may be available in each symbol period.Each resource element may cover one subcarrier in one symbol period andmay be used to send one modulation symbol, which may be a real orcomplex value. Resource elements not used for a reference signal in eachsymbol period may be arranged into resource element groups (REGs). EachREG may include four resource elements in one symbol period. The PCFICHmay occupy four REGs, which may be spaced approximately equally acrossfrequency, in symbol period 0. The PHICH may occupy three REGs, whichmay be spread across frequency, in one or more configurable symbolperiods. For example, the three REGs for the PHICH may all belong insymbol period 0 or may be spread in symbol periods 0, 1 and 2. The PDCCHmay occupy 9, 18, 32 or 64 REGs, which may be selected from theavailable REGs, in the first M symbol periods. Only certain combinationsof REGs may be allowed for the PDCCH.

A UE may know the specific REGs used for the PHICH and the PCFICH. TheUE may search different combinations of REGs for the PDCCH. The numberof combinations to search is typically less than the number of allowedcombinations for the PDCCH. An eNB may send the PDCCH to the UE in anyof the combinations that the UE will search.

FIG. 4 is a block diagram conceptually illustrating an exemplary framestructure in uplink Long Term Evolution (LTE) communications. Theavailable Resource Blocks (RBs) for the uplink may be partitioned into adata section and a control section. The control section may be formed atthe two edges of the system bandwidth and may have a configurable size.The resource blocks in the control section may be assigned to UEs fortransmission of control information. The data section may include allresource blocks not included in the control section. The design in FIG.4 results in the data section including contiguous subcarriers, whichmay allow a single UE to be assigned all of the contiguous subcarriersin the data section.

A UE may be assigned resource blocks in the control section to transmitcontrol information to an eNB. The UE may also be assigned resourceblocks in the data section to transmit data to the eNodeB. The UE maytransmit control information in a Physical Uplink Control Channel(PUCCH) on the assigned resource blocks in the control section. The UEmay transmit only data or both data and control information in aPhysical Uplink Shared Channel (PUSCH) on the assigned resource blocksin the data section. An uplink transmission may span both slots of asubframe and may hop across frequency as shown in FIG. 4.

The PSS, SSS, CRS, PBCH, PUCCH and PUSCH in LTE are described in 3GPP TS36.211, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA);Physical Channels and Modulation,” which is publicly available.

In an aspect, described herein are systems and methods for providingsupport within a wireless communication environment, such as a 3GPP LTEenvironment or the like, to facilitate multi-radio coexistencesolutions.

Referring now to FIG. 5, illustrated is an example wirelesscommunication environment 500 in which various aspects described hereincan function. The wireless communication environment 500 can include awireless device 510, which can be capable of communicating with multiplecommunication systems. These systems can include, for example, one ormore cellular systems 520 and/or 530, one or more WLAN systems 540and/or 550, one or more wireless personal area network (WPAN) systems560, one or more broadcast systems 570, one or more satellitepositioning systems 580, other systems not shown in FIG. 5, or anycombination thereof. It should be appreciated that in the followingdescription the terms “network” and “system” are often usedinterchangeably.

The cellular systems 520 and 530 can each be a CDMA, TDMA, FDMA, OFDMA,Single Carrier FDMA (SC-FDMA), or other suitable system. A CDMA systemcan implement a radio technology such as Universal Terrestrial RadioAccess (UTRA), cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) andother variants of CDMA. Moreover, cdma2000 covers IS-2000 (CDMA2000 1X),IS-95 and IS-856 (HRPD) standards. A TDMA system can implement a radiotechnology such as Global System for Mobile Communications (GSM),Digital Advanced Mobile Phone System (D-AMPS), etc. An OFDMA system canimplement a radio technology such as Evolved UTRA (E-UTRA), Ultra MobileBroadband (UMB), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM®, etc.UTRA and E-UTRA are part of Universal Mobile Telecommunication System(UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are newreleases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSMare described in documents from an organization named “3rd GenerationPartnership Project” (3GPP). cdma2000 and UMB are described in documentsfrom an organization named “3rd Generation Partnership Project 2”(3GPP2). In an aspect, the cellular system 520 can include a number ofbase stations 522, which can support bi-directional communication forwireless devices within their coverage. Similarly, the cellular system530 can include a number of base stations 532 that can supportbi-directional communication for wireless devices within their coverage.

WLAN systems 540 and 550 can respectively implement radio technologiessuch as IEEE 802.11 (WiFi), Hiperlan, etc. The WLAN system 540 caninclude one or more access points 542 that can support bi-directionalcommunication. Similarly, the WLAN system 550 can include one or moreaccess points 552 that can support bi-directional communication. TheWPAN system 560 can implement a radio technology such as Bluetooth (BT),IEEE 802.15, etc. Further, the WPAN system 560 can supportbi-directional communication for various devices such as wireless device510, a headset 562, a computer 564, a mouse 566, or the like.

The broadcast system 570 can be a television (TV) broadcast system, afrequency modulation (FM) broadcast system, a digital broadcast system,etc. A digital broadcast system can implement a radio technology such asMediaFLO™ Digital Video Broadcasting for Handhelds (DVB-H), IntegratedServices Digital Broadcasting for Terrestrial Television Broadcasting(ISDB-T), or the like. Further, the broadcast system 570 can include oneor more broadcast stations 572 that can support one-way communication.

The satellite positioning system 580 can be the United States GlobalPositioning System (GPS), the European Galileo system, the RussianGLONASS system, the Quasi-Zenith Satellite System (QZSS) over Japan, theIndian Regional Navigational Satellite System (IRNSS) over India, theBeidou system over China, and/or any other suitable system. Further, thesatellite positioning system 580 can include a number of satellites 582that transmit signals for position determination.

In an aspect, the wireless device 510 can be stationary or mobile andcan also be referred to as a user equipment (UE), a mobile station, amobile equipment, a terminal, an access terminal, a subscriber unit, astation, etc. The wireless device 510 can be cellular phone, a personaldigital assistance (PDA), a wireless modem, a handheld device, a laptopcomputer, a cordless phone, a wireless local loop (WLL) station, etc. Inaddition, a wireless device 510 can engage in two-way communication withthe cellular system 520 and/or 530, the WLAN system 540 and/or 550,devices with the WPAN system 560, and/or any other suitable systems(s)and/or devices(s). The wireless device 510 can additionally oralternatively receive signals from the broadcast system 570 and/orsatellite positioning system 580. In general, it can be appreciated thatthe wireless device 510 can communicate with any number of systems atany given moment. Also, the wireless device 510 may experiencecoexistence issues among various ones of its constituent radio devicesthat operate at the same time. Accordingly, device 510 includes acoexistence manager (CxM, not shown) that has a functional module todetect and mitigate coexistence issues, as explained further below.

Turning next to FIG. 6, a block diagram is provided that illustrates anexample design for a multi-radio wireless device 600 and may be used asan implementation of the radio 510 of FIG. 5. As FIG. 6 illustrates, thewireless device 600 can include N radios 620 a through 620 n, which canbe coupled to N antennas 610 a through 610 n, respectively, where N canbe any integer value. It should be appreciated, however, that respectiveradios 620 can be coupled to any number of antennas 610 and thatmultiple radios 620 can also share a given antenna 610.

In general, a radio 620 can be a unit that radiates or emits energy inan electromagnetic spectrum, receives energy in an electromagneticspectrum, or generates energy that propagates via conductive means. Byway of example, a radio 620 can be a unit that transmits a signal to asystem or a device or a unit that receives signals from a system ordevice. Accordingly, it can be appreciated that a radio 620 can beutilized to support wireless communication. In another example, a radio620 can also be a unit (e.g., a screen on a computer, a circuit board,etc.) that emits noise, which can impact the performance of otherradios. Accordingly, it can be further appreciated that a radio 620 canalso be a unit that emits noise and interference without supportingwireless communication.

In an aspect, respective radios 620 can support communication with oneor more systems. Multiple radios 620 can additionally or alternativelybe used for a given system, e.g., to transmit or receive on differentfrequency bands (e.g., cellular and PCS bands).

In another aspect, a digital processor 630 can be coupled to radios 620a through 620 n and can perform various functions, such as processingfor data being transmitted or received via the radios 620. Theprocessing for each radio 620 can be dependent on the radio technologysupported by that radio and can include encryption, encoding,modulation, etc., for a transmitter; demodulation, decoding, decryption,etc., for a receiver, or the like. In one example, the digital processor630 can include a coexistence manager (C×M) 640 that can controloperation of the radios 620 in order to improve the performance of thewireless device 600 as generally described herein. The coexistencemanager 640 can have access to a database 644, which can storeinformation used to control the operation of the radios 620. Asexplained further below, the coexistence manager 640 can be adapted fora variety of techniques to decrease interference between the radios. Inone example, the coexistence manager 640 requests a measurement gappattern or DRX cycle that allows an ISM radio to communicate duringperiods of LTE inactivity.

For simplicity, digital processor 630 is shown in FIG. 6 as a singleprocessor. However, it should be appreciated that the digital processor630 can include any number of processors, controllers, memories, etc. Inone example, a controller/processor 650 can direct the operation ofvarious units within the wireless device 600. Additionally oralternatively, a memory 652 can store program codes and data for thewireless device 600. The digital processor 630, controller/processor650, and memory 652 can be implemented on one or more integratedcircuits (ICs), application specific integrated circuits (ASICs), etc.By way of specific, non-limiting example, the digital processor 630 canbe implemented on a Mobile Station Modem (MSM) ASIC.

In an aspect, the coexistence manager 640 can manage operation ofrespective radios 620 utilized by wireless device 600 in order to avoidinterference and/or other performance degradation associated withcollisions between respective radios 620. The coexistence manager 640may perform one or more processes, such as those illustrated in FIG. 13.By way of further illustration, a graph 700 in FIG. 7 representsrespective potential collisions between seven example radios in a givendecision period. In the example shown in graph 700, the seven radiosinclude a WLAN transmitter (Tw), an LTE transmitter (Tl), an FMtransmitter (Tf), a GSM/WCDMA transmitter (Tc/Tw), an LTE receiver (Rl),a Bluetooth receiver (Rb), and a GPS receiver (Rg). The fourtransmitters are represented by four nodes on the left side of the graph700. The four receivers are represented by three nodes on the right sideof the graph 700.

A potential collision between a transmitter and a receiver isrepresented on the graph 700 by a branch connecting the node for thetransmitter and the node for the receiver. Accordingly, in the exampleshown in the graph 700, collisions may exist between (1) the WLANtransmitter (Tw) and the Bluetooth receiver (Rb); (2) the LTEtransmitter (Tl) and the Bluetooth receiver (Rb); (3) the WLANtransmitter (Tw) and the LTE receiver (Rl); (4) the FM transmitter (Tf)and the GPS receiver (Rg); (5) a WLAN transmitter (Tw), a GSM/WCDMAtransmitter (Tc/Tw), and a GPS receiver (Rg).

In one aspect, an example coexistence manager 640 can operate in time ina manner such as that shown by diagram 800 in FIG. 8. As diagram 800illustrates, a timeline for coexistence manager operation can be dividedinto Decision Units (DUs), which can be any suitable uniform ornon-uniform length (e.g., 100 μs) where notifications are processed, anda response phase (e.g., 20 μs) where commands are provided to variousradios 620 and/or other operations are performed based on actions takenin the evaluation phase. In one example, the timeline shown in thediagram 800 can have a latency parameter defined by a worst caseoperation of the timeline, e.g., the timing of a response in the casethat a notification is obtained from a given radio immediately followingtermination of the notification phase in a given DU.

As shown in FIG. 9, Long Term Evolution (LTE) in band 7 (for frequencydivision duplex (FDD) uplink), band 40 (for time division duplex (TDD)communication), and band 38 (for TDD downlink) is adjacent to the 2.4GHz Industrial Scientific and Medical (ISM) band used by Bluetooth (BT)and Wireless Local Area Network (WLAN) technologies. Frequency planningfor these bands is such that there is limited or no guard bandpermitting traditional filtering solutions to avoid interference atadjacent frequencies. For example, a 20 MHz guard band exists betweenISM and band 7, but no guard band exists between ISM and band 40.

To be compliant with appropriate standards, communication devicesoperating over a particular band are to be operable over the entirespecified frequency range. For example, in order to be LTE compliant, amobile station/user equipment should be able to communicate across theentirety of both band 40 (2300-2400 MHz) and band 7 (2500-2570 MHz) asdefined by the 3rd Generation Partnership Project (3GPP). Without asufficient guard band, devices employ filters that overlap into otherbands causing band interference. Because band 40 filters are 100 MHzwide to cover the entire band, the rollover from those filters crossesover into the ISM band causing interference. Similarly, ISM devices thatuse the entirety of the ISM band (e.g., from 2401 through approximately2480 MHz) will employ filters that rollover into the neighboring band 40and band 7 and may cause interference.

In-device coexistence problems can exist with respect to a UE betweenresources such as, for example, LTE and ISM bands (e.g., forBluetooth/WLAN). In current LTE implementations, any interference issuesto LTE are reflected in the downlink measurements (e.g., ReferenceSignal Received Quality (RSRQ) metrics, etc.) reported by a UE and/orthe downlink error rate which the eNB can use to make inter-frequency orinter-RAT handoff decisions to, e.g., move LTE to a channel or RAT withno coexistence issues. However, it can be appreciated that theseexisting techniques will not work if, for example, the LTE uplink iscausing interference to Bluetooth/WLAN but the LTE downlink does not seeany interference from Bluetooth/WLAN. More particularly, even if the UEautonomously moves itself to another channel on the uplink, the eNB canin some cases handover the UE back to the problematic channel for loadbalancing purposes. In any case, it can be appreciated that existingtechniques do not facilitate use of the bandwidth of the problematicchannel in the most efficient way.

Turning now to FIG. 10, a block diagram of a system 1000 for providingsupport within a wireless communication environment for multi-radiocoexistence management is illustrated. In an aspect, the system 1000 caninclude one or more UEs 1010 and/or eNBs 1040, which can engage inuplink and/or downlink communications, and/or any other suitablecommunication with each other and/or any other entities in the system1000. In one example, the UE 1010 and/or eNB 1040 can be operable tocommunicate using a variety resources, including frequency channels andsub-bands, some of which can potentially be colliding with other radioresources (e.g., a broadband radio such as an LTE modem). Thus, the UE1010 can utilize various techniques for managing coexistence betweenmultiple radios utilized by the UE 1010, as generally described herein.

To mitigate at least the above shortcomings, the UE 1010 can utilizerespective features described herein and illustrated by the system 1000to facilitate support for multi-radio coexistence within the UE 1010.For example, a channel monitoring module 1012 for monitoringcommunication channels and a communication halting module fortemporarily terminating communications on a radio access technology maybe provided. The various modules 1012-1014 may, in some examples, beimplemented as part of a coexistence manager such as the coexistencemanager 640 of FIG. 6. The various modules 1012-1014 and others may beconfigured to implement the embodiments discussed herein.

In a multi-radio device, one radio in the device may cause interferencewith another radio in the device, particularly if the radios communicateusing adjacent bandwidths. Specifically, transmission by one radio mayinterfere with reception by another. A number of solutions may beemployed to manage coexistence issues. These solutions commonly addressthe cross-radio interference problem by addressing the performance ofthe radios individually. In certain circumstances, however, multipleradios on a device may be operating together as part of a singleend-to-end communication link. For example, if a user on a mobile deviceis watching a streaming video or listening to streaming audio, theaudio/video data may be arriving via downlink on one radio (for example,LTE), with another signal, such as an audio signal, being sent viaanother radio (such as Bluetooth) to a user device, such as wirelessheadphones. In this scenario, Bluetooth and LTE operate simultaneously.In another example, a mobile device may act as an internet “hotspot” aswith a Soft Access Point configuration. In the Soft Access Pointconfiguration, a terminal (operating as an access point) communicateswith local devices using WLAN but connects to the internet using LTErather than through a hard wired cable, i.e., wireless backhaul usingLTE. In this scenario LTE and WLAN operate simultaneously.

Multiple Radio End-to-End Communications

When two or more radio access technologies are linked together in anend-to-end communication, performance of each radio in conjunction withthe other should be accounted for when addressing coexistence issues.For example, when performing power backoff on one radio to avoidinterference with the other, the level of backoff should permit bothradios to operate to achieve a desirable level of overall performancefor the end-to-end communications.

Offered is a method to manage coexistence issues for a multi-radiodevice where multiple radios are involved in the same end-to-endcommunication link, but may potentially interfere with each other. Aperformance metric may be evaluated to monitor end-to-end communicationperformance. Operation of each of the radios may be adjusted to achievea desirable level of the performance metric. The metric may be measuredwith a single loop monitoring communication performance or multipleloops may be used depending on desired performance.

For illustration purposes, a Soft Access Point communication system isdescribed, but other multiple radio end-to-end communicationconfigurations may benefit from the aspects described here. FIG. 11shows a sample Soft Access Point communication configuration. A mobiledevice 1102 contains an LTE radio 1108, where the mobile device isoperating as a user equipment (UE). The mobile device 1102 also containsa WLAN radio 1106 where the WLAN radio is operating as a mobile accesspoint (AP). As part of the Soft Access Point configuration, the WLANradio 1106 communicates with a station 1112. The mobile device's LTEradio 1108 communicates with base stations (eNBs) 1110 as a backhaul.The backhaul link may experience interference 1120 from the WLANtransmission. In Soft Access Point communications, the LTEcommunications utilize TDD downlink communications in Band 40. WLANtransmissions may interfere with LTE downlink communications due to theproximity of Band 40 with the ISM band as discussed above and shown inFIG. 9.

To manage potential interference, a coexistence manager may implementpower backoff on the WLAN transmissions, where the power of the WLANradio is lowered to prevent interference to the LTE radio. However anyreduction to WLAN transmit power comes with a corresponding reduction inWLAN throughput, and may damage the WLAN radio's ability to communicatewith WLAN stations. The goal thus becomes to improve the overallthroughput of the communication link while managing performance of boththe WLAN and LTE radios. Too much power backoff may hurt WLAN accesspoint communications, but too little (or no) power backoff may hurt theLTE backhaul communications.

In a mobile device, LTE and WLAN may share a common buffer, shown inFIG. 11 as the buffer 1104. Communications coming into the mobile deviceon a communication link from LTE downlink enter the buffer, and theinformation is output from the buffer 1104 through the WLAN radio to thedestination station 1112. The status of this buffer 1104 may bemonitored to ensure LTE and WLAN operate within certain bufferguidelines, to approach equalized communication between the LTE backhauland the WLAN access link.

As discussed herein, when measuring LTE downlink throughput, adistinction is made between LTE downlink data intended for theend-to-end communications link shared with WLAN (such as in a SoftAccess Point configuration) and LTE downlink data intended for otherapplications. The methods described herein for equalized communicationare intended to equalize throughput of LTE downlink data for the sharedend-to-end communication link and the achievable WLAN throughpututilized for the shared end-to-end communication link.

To manage the timing of asynchronous communications, such as those froma WLAN radio, special messaging may be used between a UE mobile stationand other WLAN stations. Such special messaging may be used by the UE,particularly when operating in access point (AP) mode, to control whenthe UE should expect packets from the remote station. It is undesirableto receive WLAN packets during an LTE uplink transmission as such LTEuplink transmission may interfere with and desense the receive WLANpackets. Simultaneous WLAN and LTE transmission, however, may beacceptable.

To align WLAN receive communications to avoid overlap with LTE transmitcommunications, an IEEE 802.11 feature called CTS-to-Self may be used. ACTS (clear to send)-to-Self signal indicates to a remote station whenthe access point is unable to receive a communication from the remotestation. The UE may time a CTS-to-Self message to control timing of WLANreceptions so they do not overlap with LTE transmit communications. Thatis, the CTS-to-Self message can align the WLAN receptions so they do notoverlap with timeslots allocated for LTE uplink periods. The CTS-to-Selfmessage may be ready to send a guard time ahead of LTE uplinkcommunications, as shown in FIG. 12.

FIG. 12 shows aligning of wireless communication according to one aspectof the present disclosure. Periods of LTE uplink communications areshown during times 1202. A CTS-to-Self message may be ready at time1204, a certain guard time T_(g) ahead of when LTE uplink communicationsare set to begin. The CTS-to-Self message is then sent at a time T_(s)ahead of when LTE uplink communications are set to be begin. The WLANchannel is then unavailable for a certain period of time until the WLANradio again opens the communication channel, upon expiration of theCTS-to Self message. In this manner WLAN receive communications may beshielded from potential interference from LTE transmissions. The guardtimes T_(g) and T_(s) ensure the message is received with a sufficientmargin to enable proper communications in view of the LTE timing.

In one aspect, the CTS-to-self signaling may be employed only when acoexistence manager determines that potential interference may occurwithout the signaling, based on a potential interference metric. Thepotential interference metric may indicate when an LTE transmitcommunication is likely to desense a WLAN receive communication due toproximate frequencies, overlapping times, etc.

As shown in FIG. 13 a UE may actively communication on a first radioaccess technology (RAT) as part of an end-to-end communication link, asshown in block 1302. A UE may actively communicate on a second RAT aspart of the end-to-end communication link, as shown in block 1304. TheUE may send a message instructing a remote device on the second RAT totemporarily stop transmission, as shown in block 1306. The message maybe sent at a time calculated to prevent transmission from the remotedevice from being received during an uplink transmission of the firstRAT in the end-to-end communication link.

FIG. 14 is a diagram illustrating an example of a hardwareimplementation for an apparatus 1400 employing a coexistence managementsystem 1414. The coexistence management system 1414 may be implementedwith a bus architecture, represented generally by a bus 1424. The bus1424 may include any number of interconnecting buses and bridgesdepending on the specific application of the coexistence managementsystem 1414 and the overall design constraints. The bus 1424 linkstogether various circuits including one or more processors and/orhardware modules, represented by a processor 1426, a communicationmodule 1402, an instructing module 1404, and a computer-readable medium1428. The bus 1424 may also link various other circuits such as timingsources, peripherals, voltage regulators, and power management circuits,which are well known in the art, and therefore, will not be describedany further.

The apparatus includes the coexistence management system 1414 coupled toa transceiver 1422. The transceiver 1422 is coupled to one or moreantennas 1420. The transceiver 1422 provides a means for communicatingwith various other apparatus over a transmission medium. The coexistencemanagement system 1414 includes the processor 1426 coupled to thecomputer-readable medium 1428. The processor 1426 is responsible forgeneral processing, including the execution of software stored on thecomputer-readable medium 1428. The software, when executed by theprocessor 1426, causes the coexistence management system 1414 to performthe various functions described supra for any particular apparatus. Thecomputer-readable medium 1428 may also be used for storing data that ismanipulated by the processor 1426 when executing software. Thecoexistence management system 1414 further includes the communicationmodule 1402 for actively communicating on a first RAT and a second RAT.The coexistence management system 1414 further includes the instructingmodule 1404 for sending a message instructing a remote device on thesecond RAT to temporarily stop transmission. The message may be sent ata time calculated to prevent transmission from the remote device frombeing received during an uplink transmission of the first RAT in theend-to-end communication link. The communication module 1402 and theinstructing module 1404 may be software modules running in the processor1426, resident/stored in the computer readable medium 1428, one or morehardware modules coupled to the processor 1426, or some combinationthereof. The coexistence management system 1414 may be a component ofthe UE 250 and may include the memory 272 and/or the processor 270.

In one configuration, the apparatus 1400 for wireless communicationincludes means for communicating and means for sending. The means may bethe communication module 1402, the instructing module 1404, and/or thecoexistence management system 1414 of the apparatus 1400 configured toperform the functions recited by the measuring and recording means. Asdescribed above, the coexistence management system 1414 may include thechannel halting module 1014, the coexistence manager 640, the memory272, the processor 270, the antennae 252 a-252 r, thereceiver/transmitter 254 a-254 r, the radios 620 a-620 n, thecontroller/processor 650, the memory 652, the antennae 610 a-610 n, thedigital processor 630, and/or the database 644. In another aspect, theaforementioned means may be any module or any apparatus configured toperform the functions recited by the aforementioned means.

The examples above describe aspects implemented in an LTE system.However, the scope of the disclosure is not so limited. Various aspectsmay be adapted for use with other communication systems, such as thosethat employ any of a variety of communication protocols including, butnot limited to, CDMA systems, TDMA systems, FDMA systems, and OFDMAsystems.

It is understood that the specific order or hierarchy of steps in theprocesses disclosed is an example of exemplary approaches. Based upondesign preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged while remainingwithin the scope of the present disclosure. The accompanying methodclaims present elements of the various steps in a sample order, and arenot meant to be limited to the specific order or hierarchy presented.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the aspects disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. Toclearly illustrate this interchangeability of hardware and software,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or softwaredepends upon the particular application and design constraints imposedon the overall system. Skilled artisans may implement the describedfunctionality in varying ways for each particular application, but suchimplementation decisions should not be interpreted as causing adeparture from the scope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the aspects disclosed herein may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with theaspects disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such the processorcan read information from, and write information to, the storage medium.In the alternative, the storage medium may be integral to the processor.The processor and the storage medium may reside in an ASIC. The ASIC mayreside in a user terminal. In the alternative, the processor and thestorage medium may reside as discrete components in a user terminal.

The previous description of the disclosed aspects is provided to enableany person skilled in the art to make or use the present disclosure.Various modifications to these aspects will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other aspects without departing from the spirit or scope ofthe disclosure. Thus, the present disclosure is not intended to belimited to the aspects shown herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method of wireless communication by anapparatus, comprising: actively communicating on a first radio accesstechnology (RAT) as part of an end-to-end communication link; activelycommunicating on a second RAT as part of the end-to-end communicationlink; and sending a message instructing a remote device on the secondRAT to temporarily stop transmission, the message being sent at a timecalculated to prevent transmission from the remote device from beingreceived during an uplink transmission of the first RAT in theend-to-end communication link, in which the message comprises aCTS-to-Self message to indicate to the remote device when the apparatusis unable to receive communication from the remote device on the secondRAT, and the time that the CTS-to-Self message is sent is a guard timeahead of the uplink transmission of the first RAT.
 2. The method ofclaim 1 in which the sending is based at least in part on an indicationof potential interference between uplink transmission of the first RATand downlink communications of the second RAT.
 3. The method of claim 1in which the active communications on the first RAT and the activecommunications on the second RAT are by a user equipment operating in anaccess point (AP) mode.
 4. An apparatus for wireless communication,comprising: means for actively communicating on a first radio accesstechnology (RAT) as part of an end-to-end communication link; means foractively communicating on a second RAT as part of the end-to-endcommunication link; and means for sending a message instructing a remotedevice on the second RAT to temporarily stop transmission, the messagebeing sent at a time calculated to prevent transmission from the remotedevice from being received during an uplink transmission of the firstRAT in the end-to-end communication link, in which the message comprisesa CTS-to-Self message to indicate to the remote device when theapparatus is unable to receive communication from the remote device onthe second RAT, and the time that the CTS-to-Self message is sent is aguard time ahead of the uplink transmission of the first RAT.
 5. Theapparatus of claim 4 in which the means for sending is based at least inpart on an indication of potential interference between uplinktransmission of the first RAT and downlink communications of the secondRAT.
 6. The apparatus of claim 4 in which the active communications onthe first RAT and the active communications on the second RAT are by auser equipment operating in an access point (AP) mode.
 7. A computerprogram product configured for an apparatus for wireless communications,the computer program product comprising: a non-transitorycomputer-readable medium having non-transitory program code recordedthereon, the program code comprising: program code to activelycommunicate on a first radio access technology (RAT) as part of anend-to-end communication link; program code to actively communicate on asecond RAT as part of the end-to-end communication link; and programcode to send a message instructing a remote device on the second RAT totemporarily stop transmission, the message being sent at a timecalculated to prevent transmission from the remote device from beingreceived during an uplink transmission of the first RAT in theend-to-end communication link, in which the message comprises aCTS-to-Self message to indicate to the remote device when the apparatusis unable to receive communication from the remote device on the secondRAT, and the time that the CTS-to-Self message is sent is a guard timeahead of the uplink transmission of the first RAT.
 8. The computerprogram product of claim 7 in which the program code to send is based atleast in part on an indication of potential interference between uplinktransmission of the first RAT and downlink communications of the secondRAT.
 9. The computer program product of claim 7 in which the activecommunications on the first RAT and the active communications on thesecond RAT are by a user equipment operating in an access point (AP)mode.
 10. An apparatus for wireless communication, comprising: a memory;and at least one processor coupled to the memory, the at least oneprocessor being configured: to actively communicate on a first radioaccess technology (RAT) as part of an end-to-end communication link; toactively communicate on a second RAT as part of the end-to-endcommunication link; and to send a message instructing a remote device onthe second RAT to temporarily stop transmission, the message being sentat a time calculated to prevent transmission from the remote device frombeing received during an uplink transmission of the first RAT in theend-to-end communication link, in which the message comprises aCTS-to-Self message to indicate to the remote device when the apparatusis unable to receive communication from the remote device on the secondRAT, and the time that the CTS-to-Self message is sent is a guard timeahead of the uplink transmission of the first RAT.
 11. The apparatus ofclaim 10 in which the sending is based at least in part on an indicationof potential interference between uplink transmission of the first RATand downlink communications of the second RAT.
 12. The apparatus ofclaim 10 in which the active communications on the first RAT and theactive communications on the second RAT are by a user equipmentoperating in an access point (AP) mode.